Merge cfb293c into 65c1927

FuelLabs · Feb 16, 2024 · 057388c · 057388c
2 parents 65c1927 + cfb293c
commit 057388c
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diff --git a/docs/book/src/SUMMARY.md b/docs/book/src/SUMMARY.md
@@ -42,6 +42,7 @@
   - [Associated Types](./advanced/associated_types.md)
   - [Generics and Trait Constraints](./advanced/generics_and_trait_constraints.md)
   - [Assembly](./advanced/assembly.md)
+  - [Never Type](./advanced/never_type.md)
 - [Common Collections](./common-collections/index.md)
   - [Vectors on the Heap](./common-collections/vec.md)
   - [Storage Vectors](./common-collections/storage_vec.md)

diff --git a/docs/book/src/advanced/index.md b/docs/book/src/advanced/index.md
@@ -8,3 +8,4 @@ Advanced concepts.
 - [Associated Types](./associated_types.md)
 - [Generics and Trait Constraints](./generics_and_trait_constraints.md)
 - [Assembly](./assembly.md)
+- [Never Type](./never_type.md)
diff --git a/docs/book/src/advanced/never_type.md b/docs/book/src/advanced/never_type.md
@@ -0,0 +1,53 @@
+# Never Type
+
+The Never type `!` represents the type of computations which never resolve to any value at all.
+
+## Additional Information
+
+`break`, `continue` and `return` expressions also have type `!`. For example we are allowed to
+write:
+
+```sway
+let x: ! = {
+    return 123
+};
+```
+
+Although the `let` is pointless here, it illustrates the meaning of `!`. Since `x` is never
+assigned a value (because `return` returns from the entire function), `x` can be given type
+`Never`. We could also replace `return 123` with a `revert()` or a never-ending `loop` and this code
+would still be valid.
+
+A more realistic usage of `Never` is in this code:
+
+```sway
+let num: u32 = match get_a_number() {
+    Some(num) => num,
+    None => break,
+};
+```
+
+Both match arms must produce values of type [`u32`], but since `break` never produces a value
+at all we know it can never produce a value which isn't a [`u32`]. This illustrates another
+behaviour of the `!` type - expressions with type `!` will coerce into any other type.
+
+Note that `!` type coerces into any other type, another example of this would be:
+
+```sway
+let x: u32 = {
+    return 123
+};
+```
+
+Regardless of the type of `x`, the return block of type `Never` will always coerce into `x` type.
+
+## Examples
+
+```sway
+fn foo() {
+    let num: u64 = match Option::None::<u64> {
+        Some(num) => num,
+        None => return,
+    };
+}
+```
diff --git a/forc-plugins/forc-doc/src/tests/expects/impl_trait/mod.rs b/forc-plugins/forc-doc/src/tests/expects/impl_trait/mod.rs
@@ -37,7 +37,7 @@ fn test_impl_traits_default() {
     assert_search_js(
         &doc_path,
         &expect![[r#"
-            var SEARCH_INDEX={"core":[{"html_filename":"trait.AsRawSlice.html","module_info":["core","raw_slice"],"name":"AsRawSlice","preview":"Trait to return a type as a <code>raw_slice</code>.\n","type_name":"trait"},{"html_filename":"fn.from_str_array.html","module_info":["core","str"],"name":"from_str_array","preview":"","type_name":"function"},{"html_filename":"trait.Add.html","module_info":["core","ops"],"name":"Add","preview":"Trait for the addition of two values.\n","type_name":"trait"},{"html_filename":"trait.Subtract.html","module_info":["core","ops"],"name":"Subtract","preview":"Trait for the subtraction of two values.\n","type_name":"trait"},{"html_filename":"trait.Multiply.html","module_info":["core","ops"],"name":"Multiply","preview":"Trait for the multiplication of two values.\n","type_name":"trait"},{"html_filename":"trait.Divide.html","module_info":["core","ops"],"name":"Divide","preview":"Trait for the division of two values.\n","type_name":"trait"},{"html_filename":"trait.Mod.html","module_info":["core","ops"],"name":"Mod","preview":"Trait for the modulo of two values.\n","type_name":"trait"},{"html_filename":"trait.Not.html","module_info":["core","ops"],"name":"Not","preview":"Trait to invert a type.\n","type_name":"trait"},{"html_filename":"trait.Eq.html","module_info":["core","ops"],"name":"Eq","preview":"Trait to evaluate if two types are equal.\n","type_name":"trait"},{"html_filename":"trait.Ord.html","module_info":["core","ops"],"name":"Ord","preview":"Trait to evaluate if one value is greater or less than another of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseAnd.html","module_info":["core","ops"],"name":"BitwiseAnd","preview":"Trait to bitwise AND two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseOr.html","module_info":["core","ops"],"name":"BitwiseOr","preview":"Trait to bitwise OR two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseXor.html","module_info":["core","ops"],"name":"BitwiseXor","preview":"Trait to bitwise XOR two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.Shift.html","module_info":["core","ops"],"name":"Shift","preview":"Trait to bit shift a value.\n","type_name":"trait"},{"html_filename":"enum.Never.html","module_info":["core","never"],"name":"Never","preview":"<code>Never</code> represents the type of computations which never resolve to any value at all.","type_name":"enum"},{"html_filename":"struct.StorageKey.html","module_info":["core","storage"],"name":"StorageKey","preview":"Describes a location in storage.\n","type_name":"struct"},{"html_filename":"struct.Buffer.html","module_info":["core","codec"],"name":"Buffer","preview":"","type_name":"struct"},{"html_filename":"trait.AbiEncode.html","module_info":["core","codec"],"name":"AbiEncode","preview":"","type_name":"trait"},{"html_filename":"fn.encode.html","module_info":["core","codec"],"name":"encode","preview":"","type_name":"function"}],"impl_traits":[{"html_filename":"trait.Foo.html","module_info":["impl_traits","foo"],"name":"Foo","preview":"","type_name":"trait"},{"html_filename":"trait.Baz.html","module_info":["impl_traits","foo"],"name":"Baz","preview":"","type_name":"trait"},{"html_filename":"struct.Bar.html","module_info":["impl_traits","bar"],"name":"Bar","preview":"","type_name":"struct"}]};
+            var SEARCH_INDEX={"core":[{"html_filename":"trait.AsRawSlice.html","module_info":["core","raw_slice"],"name":"AsRawSlice","preview":"Trait to return a type as a <code>raw_slice</code>.\n","type_name":"trait"},{"html_filename":"fn.from_str_array.html","module_info":["core","str"],"name":"from_str_array","preview":"","type_name":"function"},{"html_filename":"trait.Add.html","module_info":["core","ops"],"name":"Add","preview":"Trait for the addition of two values.\n","type_name":"trait"},{"html_filename":"trait.Subtract.html","module_info":["core","ops"],"name":"Subtract","preview":"Trait for the subtraction of two values.\n","type_name":"trait"},{"html_filename":"trait.Multiply.html","module_info":["core","ops"],"name":"Multiply","preview":"Trait for the multiplication of two values.\n","type_name":"trait"},{"html_filename":"trait.Divide.html","module_info":["core","ops"],"name":"Divide","preview":"Trait for the division of two values.\n","type_name":"trait"},{"html_filename":"trait.Mod.html","module_info":["core","ops"],"name":"Mod","preview":"Trait for the modulo of two values.\n","type_name":"trait"},{"html_filename":"trait.Not.html","module_info":["core","ops"],"name":"Not","preview":"Trait to invert a type.\n","type_name":"trait"},{"html_filename":"trait.Eq.html","module_info":["core","ops"],"name":"Eq","preview":"Trait to evaluate if two types are equal.\n","type_name":"trait"},{"html_filename":"trait.Ord.html","module_info":["core","ops"],"name":"Ord","preview":"Trait to evaluate if one value is greater or less than another of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseAnd.html","module_info":["core","ops"],"name":"BitwiseAnd","preview":"Trait to bitwise AND two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseOr.html","module_info":["core","ops"],"name":"BitwiseOr","preview":"Trait to bitwise OR two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.BitwiseXor.html","module_info":["core","ops"],"name":"BitwiseXor","preview":"Trait to bitwise XOR two values of the same type.\n","type_name":"trait"},{"html_filename":"trait.Shift.html","module_info":["core","ops"],"name":"Shift","preview":"Trait to bit shift a value.\n","type_name":"trait"},{"html_filename":"struct.StorageKey.html","module_info":["core","storage"],"name":"StorageKey","preview":"Describes a location in storage.\n","type_name":"struct"},{"html_filename":"struct.Buffer.html","module_info":["core","codec"],"name":"Buffer","preview":"","type_name":"struct"},{"html_filename":"trait.AbiEncode.html","module_info":["core","codec"],"name":"AbiEncode","preview":"","type_name":"trait"},{"html_filename":"fn.encode.html","module_info":["core","codec"],"name":"encode","preview":"","type_name":"function"}],"impl_traits":[{"html_filename":"trait.Foo.html","module_info":["impl_traits","foo"],"name":"Foo","preview":"","type_name":"trait"},{"html_filename":"trait.Baz.html","module_info":["impl_traits","foo"],"name":"Baz","preview":"","type_name":"trait"},{"html_filename":"struct.Bar.html","module_info":["impl_traits","bar"],"name":"Bar","preview":"","type_name":"struct"}]};
             "object"==typeof exports&&"undefined"!=typeof module&&(module.exports=SEARCH_INDEX);"#]],
     );
     assert_file_tree(
@@ -50,8 +50,6 @@ fn test_impl_traits_default() {
             "core/codec/struct.Buffer.html",
             "core/codec/trait.AbiEncode.html",
             "core/index.html",
-            "core/never/enum.Never.html",
-            "core/never/index.html",
             "core/ops/index.html",
             "core/ops/trait.Add.html",
             "core/ops/trait.BitwiseAnd.html",

diff --git a/sway-ast/src/ty/mod.rs b/sway-ast/src/ty/mod.rs
@@ -26,6 +26,9 @@ pub enum Ty {
         ampersand_token: AmpersandToken,
         ty: Box<Ty>,
     },
+    Never {
+        bang_token: BangToken,
+    },
 }
 
 impl Spanned for Ty {
@@ -43,6 +46,7 @@ impl Spanned for Ty {
                 ampersand_token,
                 ty,
             } => Span::join(ampersand_token.span(), ty.span()),
+            Ty::Never { bang_token } => bang_token.span(),
         }
     }
 }

diff --git a/sway-core/src/abi_generation/evm_abi.rs b/sway-core/src/abi_generation/evm_abi.rs
@@ -83,6 +83,7 @@ pub fn abi_str(type_info: &TypeInfo, type_engine: &TypeEngine, decl_engine: &Dec
     use TypeInfo::*;
     match type_info {
         Unknown => "unknown".into(),
+        Never => "never".into(),
         UnknownGeneric { name, .. } => name.to_string(),
         Placeholder(_) => "_".to_string(),
         TypeParam(n) => format!("typeparam({n})"),

diff --git a/sway-core/src/abi_generation/fuel_abi.rs b/sway-core/src/abi_generation/fuel_abi.rs
@@ -807,6 +807,7 @@ impl TypeInfo {
         use TypeInfo::*;
         match self {
             Unknown => "unknown".into(),
+            Never => "never".into(),
             UnknownGeneric { name, .. } => name.to_string(),
             Placeholder(_) => "_".to_string(),
             TypeParam(n) => format!("typeparam({n})"),

diff --git a/sway-core/src/asm_generation/fuel/fuel_asm_builder.rs b/sway-core/src/asm_generation/fuel/fuel_asm_builder.rs
@@ -1728,6 +1728,7 @@ impl<'ir, 'eng> FuelAsmBuilder<'ir, 'eng> {
     // XXX reassess all the places we use this
     pub(crate) fn is_copy_type(&self, ty: &Type) -> bool {
         ty.is_unit(self.context)
+            || ty.is_never(self.context)
             || ty.is_bool(self.context)
             || ty
                 .get_uint_width(self.context)

diff --git a/sway-core/src/ir_generation/convert.rs b/sway-core/src/ir_generation/convert.rs
@@ -159,6 +159,7 @@ fn convert_resolved_type(
             convert_resolved_typeid(type_engine, decl_engine, context, &ty.type_id, span)?
         }
         TypeInfo::Ref(_) => Type::get_uint64(context),
+        TypeInfo::Never => Type::get_never(context),
 
         // Unsupported types which shouldn't exist in the AST after type checking and
         // monomorphisation.

diff --git a/sway-core/src/language/ty/ast_node.rs b/sway-core/src/language/ty/ast_node.rs
@@ -135,18 +135,6 @@ impl CollectTypesMetadata for TyAstNode {
     }
 }
 
-impl DeterministicallyAborts for TyAstNode {
-    fn deterministically_aborts(&self, decl_engine: &DeclEngine, check_call_body: bool) -> bool {
-        use TyAstNodeContent::*;
-        match &self.content {
-            Declaration(_) => false,
-            Expression(exp) => exp.deterministically_aborts(decl_engine, check_call_body),
-            SideEffect(_) => false,
-            Error(_, _) => false,
-        }
-    }
-}
-
 impl GetDeclIdent for TyAstNode {
     fn get_decl_ident(&self) -> Option<Ident> {
         self.content.get_decl_ident()

diff --git a/sway-core/src/language/ty/code_block.rs b/sway-core/src/language/ty/code_block.rs
@@ -5,7 +5,7 @@ use sway_types::Span;
 
 use crate::{
     decl_engine::*, engine_threading::*, language::ty::*, semantic_analysis::TypeCheckContext,
-    type_system::*, types::DeterministicallyAborts,
+    type_system::*,
 };
 
 #[derive(Clone, Debug)]
@@ -74,11 +74,3 @@ impl UpdateConstantExpression for TyCodeBlock {
             .for_each(|x| x.update_constant_expression(engines, implementing_type));
     }
 }
-
-impl DeterministicallyAborts for TyCodeBlock {
-    fn deterministically_aborts(&self, decl_engine: &DeclEngine, check_call_body: bool) -> bool {
-        self.contents
-            .iter()
-            .any(|x| x.deterministically_aborts(decl_engine, check_call_body))
-    }
-}
diff --git a/sway-core/src/language/ty/expression/expression.rs b/sway-core/src/language/ty/expression/expression.rs
@@ -317,109 +317,6 @@ impl CollectTypesMetadata for TyExpression {
     }
 }
 
-impl DeterministicallyAborts for TyExpression {
-    fn deterministically_aborts(&self, decl_engine: &DeclEngine, check_call_body: bool) -> bool {
-        use TyExpressionVariant::*;
-        match &self.expression {
-            FunctionApplication {
-                fn_ref, arguments, ..
-            } => {
-                if !check_call_body {
-                    return false;
-                }
-                let function_decl = decl_engine.get_function(fn_ref);
-                function_decl
-                    .body
-                    .deterministically_aborts(decl_engine, check_call_body)
-                    || arguments
-                        .iter()
-                        .any(|(_, x)| x.deterministically_aborts(decl_engine, check_call_body))
-            }
-            Tuple { fields, .. } => fields
-                .iter()
-                .any(|x| x.deterministically_aborts(decl_engine, check_call_body)),
-            Array { contents, .. } => contents
-                .iter()
-                .any(|x| x.deterministically_aborts(decl_engine, check_call_body)),
-            CodeBlock(contents) => contents.deterministically_aborts(decl_engine, check_call_body),
-            LazyOperator { lhs, .. } => lhs.deterministically_aborts(decl_engine, check_call_body),
-            StructExpression { fields, .. } => fields.iter().any(|x| {
-                x.value
-                    .deterministically_aborts(decl_engine, check_call_body)
-            }),
-            EnumInstantiation { contents, .. } => contents
-                .as_ref()
-                .map(|x| x.deterministically_aborts(decl_engine, check_call_body))
-                .unwrap_or(false),
-            AbiCast { address, .. } => {
-                address.deterministically_aborts(decl_engine, check_call_body)
-            }
-            StructFieldAccess { .. }
-            | Literal(_)
-            | StorageAccess { .. }
-            | VariableExpression { .. }
-            | ConstantExpression { .. }
-            | FunctionParameter
-            | TupleElemAccess { .. } => false,
-            IntrinsicFunction(kind) => kind.deterministically_aborts(decl_engine, check_call_body),
-            ArrayIndex { prefix, index } => {
-                prefix.deterministically_aborts(decl_engine, check_call_body)
-                    || index.deterministically_aborts(decl_engine, check_call_body)
-            }
-            AsmExpression { registers, .. } => registers.iter().any(|x| {
-                x.initializer
-                    .as_ref()
-                    .map(|x| x.deterministically_aborts(decl_engine, check_call_body))
-                    .unwrap_or(false)
-            }),
-            MatchExp { desugared, .. } => {
-                desugared.deterministically_aborts(decl_engine, check_call_body)
-            }
-            IfExp {
-                condition,
-                then,
-                r#else,
-                ..
-            } => {
-                condition.deterministically_aborts(decl_engine, check_call_body)
-                    || (then.deterministically_aborts(decl_engine, check_call_body)
-                        && r#else
-                            .as_ref()
-                            .map(|x| x.deterministically_aborts(decl_engine, check_call_body))
-                            .unwrap_or(false))
-            }
-            AbiName(_) => false,
-            EnumTag { exp } => exp.deterministically_aborts(decl_engine, check_call_body),
-            UnsafeDowncast { exp, .. } => {
-                exp.deterministically_aborts(decl_engine, check_call_body)
-            }
-            WhileLoop { condition, body } => {
-                condition.deterministically_aborts(decl_engine, check_call_body)
-                    || body.deterministically_aborts(decl_engine, check_call_body)
-            }
-            ForLoop { desugared } => {
-                desugared.deterministically_aborts(decl_engine, check_call_body)
-            }
-            Break => false,
-            Continue => false,
-            Reassignment(reassignment) => reassignment
-                .rhs
-                .deterministically_aborts(decl_engine, check_call_body),
-            ImplicitReturn(exp) => exp.deterministically_aborts(decl_engine, check_call_body),
-            // TODO: Is this correct?
-            // I'm not sure what this function is supposed to do exactly. It's called
-            // "deterministically_aborts" which I thought meant it checks for an abort/panic, but
-            // it's actually checking for returns.
-            //
-            // Also, is it necessary to check the expression to see if avoids the return? eg.
-            // someone could write `return break;` in a loop, which would mean the return never
-            // gets executed.
-            Return(_) => true,
-            Ref(exp) | Deref(exp) => exp.deterministically_aborts(decl_engine, check_call_body),
-        }
-    }
-}
-
 impl TyExpression {
     pub(crate) fn error(err: ErrorEmitted, span: Span, engines: &Engines) -> TyExpression {
         let type_engine = engines.te();

diff --git a/sway-core/src/language/ty/expression/intrinsic_function.rs b/sway-core/src/language/ty/expression/intrinsic_function.rs
@@ -3,9 +3,7 @@ use std::{
     hash::{Hash, Hasher},
 };
 
-use crate::{
-    decl_engine::DeclEngine, engine_threading::*, language::ty::*, type_system::*, types::*,
-};
+use crate::{engine_threading::*, language::ty::*, type_system::*, types::*};
 use itertools::Itertools;
 use sway_ast::Intrinsic;
 use sway_error::handler::{ErrorEmitted, Handler};
@@ -99,16 +97,6 @@ impl DebugWithEngines for TyIntrinsicFunctionKind {
     }
 }
 
-impl DeterministicallyAborts for TyIntrinsicFunctionKind {
-    fn deterministically_aborts(&self, decl_engine: &DeclEngine, check_call_body: bool) -> bool {
-        matches!(self.kind, Intrinsic::Revert)
-            || self
-                .arguments
-                .iter()
-                .any(|x| x.deterministically_aborts(decl_engine, check_call_body))
-    }
-}
-
 impl CollectTypesMetadata for TyIntrinsicFunctionKind {
     fn collect_types_metadata(
         &self,

diff --git a/sway-core/src/semantic_analysis.rs b/sway-core/src/semantic_analysis.rs
@@ -9,10 +9,8 @@ mod program;
 mod type_check_analysis;
 pub(crate) mod type_check_context;
 mod type_check_finalization;
-mod type_check_unification;
 pub use ast_node::*;
 pub use namespace::Namespace;
 pub(crate) use type_check_analysis::*;
 pub(crate) use type_check_context::TypeCheckContext;
 pub(crate) use type_check_finalization::*;
-pub(crate) use type_check_unification::*;